The present invention relates to an electronic key system for locking/unlocking a door of, for example, a vehicle or a house or for authorizing (allowing) starting of a vehicle engine.
Conventionally, a key using system such as a vehicle or house door locking device or an engine starter is provided with such an immobilizer function as to authorize locking/unlocking of the door or starting of the engine if an attempted communication is established between the key and the lock. In such a system, it is difficult to duplicate the key and also to unlock the door except by a regular key or start the engine, thus improving security.
By such a conventional system, however, if the regular key itself is stolen or lost, it may be used to illegally unlock the door or start the engine.